As explained in WIPO Pat. App. Pub. No. WO03033586, PE-RT materials are required to have a pressure test resistance, as determined according to DIN 16 833, of at least 165 h at 3.6 MPa and 95° C.
Moreover, they should be flexible, which translates into having an E-modulus of less than about 900 MPa.
According to WIPO Pat. App. Pub. No. WO03033586, such requirements are met by providing a multimodal polyethylene composition having a density of 0.921-0.950 g/cm3 and comprising a HMW fraction having a density of at least 0.920 g/cm3.